(19)
(11) EP 0 543 618 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
31.05.1995 Bulletin 1995/22

(43) Date of publication A2:
26.05.1993 Bulletin 1993/21

(21) Application number: 92310480.6

(22) Date of filing: 18.11.1992
(51) International Patent Classification (IPC)5: H03M 1/12, H03M 3/02
(84) Designated Contracting States:
BE DE FR IT NL

(30) Priority: 20.11.1991 GB 9124591

(71) Applicant: GEC-MARCONI LIMITED
Stanmore, Middlesex HA7 4LY (GB)

(72) Inventor:
  • Thurston, Andrew Mark
    Chelmsford, Essex CM1 5QS (GB)

(74) Representative: Waters, Jeffrey et al
The General Electric Company, p.l.c. GEC Patent Department Waterhouse Lane
Chelmsford, Essex CM1 2QX
Chelmsford, Essex CM1 2QX (GB)


(56) References cited: : 
   
       


    (54) Analogue-to-digital converter


    (57) In a conventional sigma-delta analogue-to-digital converter an input such as an i.f. signal at i/p is converted to digital form by analogue-to-digital converter 9 at output o/p, and the quantising noise is shaped by means of a feedback loop which feeds a signal derived from the digital output to be combined in analogue form with the analogue input to form a difference signal for input to filter means 6, 7, the filtered difference signal being applied to the input of the analogue-to-digital converter 9. In the invention, to improve the signal-to-noise ratio, the analogue-to-digital converter 9 has more levels of quantisation than the digital-to-analogue converter 4 but the latter is clocked at a faster rate.






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